Endocrine therapy uses hormone antagonists to greatly reduce the risk of disease recurrence in women with early-stage, estrogen-receptor (ER) positive breast cancer. However, the treatment can come with severe side effects. Around 30 per cent of women stop taking the therapy after three years largely due to these negative impacts. Usually patients receive the hormone therapy for five years following initial treatment (e.g., chemotherapy, surgery), but it can also be taken longer-term. A central question facing patients and clinicians is how to balance, in their decision making, the side effects of long-term treatment with the potential reduction in recurrence risk. In short, they want to know: ‘is it worth it?’